Valorization of Food Industry By-products from Citrus sinensis: Extraction, Encapsulation Stabilization, and Biological Evaluation of Orange Peel Essential Oils

Introduction and Aim: In the context of agro-industrial by-product valorization, this study aims to develop and evaluate an integrated approach combining extraction process optimization and encapsulation technologies. The objective is to maximize the recovery efficiency of active principles from orange peels while enhancing their stability for multi-sectoral industrial applications.

Methodology: Two extraction methods were compared: hydrodistillation and salt-assisted steam distillation (salting-out effect). The resulting essential oils (EOs) were then encapsulated within two matrices (β-cyclodextrin and polyethylene glycol [PEG 6000]) using two drying methods: freeze-drying and rotary evaporation . The systems were characterized using HPLC chromatography and Fourier-transform infrared spectroscopy (FTIR). Finally, their antioxidant capacity was evaluated through complementary assays (FRAP, and NO•).

Results: Salt-assisted steam distillation proved to be more efficient than conventional hydrodistillation, reducing extraction time and favorably preserving the chemical profile. Notably, citronellal—which was absent during hydrodistillation—was successfully detected by HPLC alongside the major compound, limonene. Regarding formulation, exceptionally high encapsulation efficiencies (> 99%) were achieved across all studied systems. Recovery yields of the complexes ranged from 67.13% to 85.31%, with mass losses attributed to processing and drying stages (freeze-drying being optimal for the β-CD/EO system, while rotary evaporation performed better for PEG/EO). FTIR spectra confirmed the absence of major chemical modifications, validating the preservation of active compounds through purely physical interactions with the matrices. Biologically, raw EOs exhibited higher antioxidant activity compared to encapsulated systems due to the reduced immediate availability of the active compounds after formulation, although certain formulations retained a partial protective effect.

Conclusion: This integrated approach demonstrates the technical feasibility of stabilizing citrus essential oils. Salt-assisted steam distillation coupled with encapsulation represents a promising pathway to preserve and valorize these high-value biomolecules.